1. Field of the Invention
The present invention relates to a metal organic vapor phase epitaxy (MOVPE) method. And the present invention relates to a method for manufacturing a semiconductor laser device, more particularly to a method for manufacturing a semiconductor laser device by MOVPE.
2. Description of the Related Art
A metal organic vapor phase epitaxy (MOVPE) method has been known as a technique for manufacturing a semiconductor laser device. Selective MOVPE realizes selective film formation. That is, a film (composition semiconductor film) is selectively formed on exposed regions which are not masked by an SiO.sub.2 film.
"IEEE Photonics Technology Letter 9 (1997) p.291" (hereinafter referred to as Document 1) discloses a technique for manufacturing a double-channel planar buried heterostructure (DC-PBH) laser diode having InGaAsP multiquantum wells (MQW) structure by the selective MOVPE.
FIGS. 9A to 9F show steps of manufacturing a semiconductor laser diode by the technique disclosed in Document 1.
First, the chemical vapor deposition is carried out to deposit an SiO.sub.2 film 180 having the thickness of 100 nm onto a (100) just oriented n-InP substrate 110, as shown in FIG. 9A.
Then, the SiO.sub.2 film 180 is patterned so as to be striped masks as shown in FIG. 9B. The mask width Wm is 8-micron wide and the width Wo of open stripe 180A is 1.5 microns wide. These stripes are extending in the [011] direction.
Then, a waveguide 120 (having the double heterostructure) containing an MQW active layer is formed by selective MOVPE on the open stripe region 180A as shown in FIG. 9C. The MQW active layer, 121 consists of 0.7% compressively strained InGaAsP wells (5-nm thick) and InGaAsP barriers (each of which has the thickness of 8 nm, and emits lights having 1.13-micron wavelength), sandwiched by InGaAsP SCH layers (each of which has the thickness of 60 nm, and emits lights having 1.13-micron wavelength).
Then, an SiO.sub.2 mask 190 is formed on the top of the waveguide 120 using a self-alignment process as shown in FIG. 9D, and the SiO.sub.2 portion other than the SiO.sub.2 mask 190 is removed.
A current-blocking layer 130 is selectively grown on the substrate 110 by selective MOVPE as shown in FIG. 9E. The current-blocking layer 130 consists of p-InP (having the carrier concentration of 3.times.10.sup.17 cm.sup.-3 and the thickness of 0.75 microns), n-InP (having the carrier concentration of 3.times.10.sup.17 cm.sup.-3 and the thickness of 0.7 microns) and p-InP (having the carrier concentration of 3.times.10.sup.18 cm.sup.-3 and the thickness of 0.10 microns) layers. Then, the SiO.sub.2 mask 190 is removed.
After the SiO.sub.2 mask 190 is removed, a p-InP cladding layer 140 is formed on the waveguide 120 and the current-blocking layer 130 as shown in FIG. 9F. Further, a p.sup.- -InGaAs contact layer 150 is formed on the p-InP cladding layer 140.
Finally, a p-type electrode 160 is formed on the p.sup.+ -InGaAs contact layer 150 and an n-type electrode 170 is formed on a back surface (a surface opposing to the surface on which the waveguide 120 is formed) of the substrate 110. Thus, the DC-PBH structure semiconductor laser diode is completed by the selective MOVPE.
Document 1 discloses the process of manufacturing the semiconductor laser diode, however, it does not suggest that the shape of the diode surface (an uneven surface or a planar surface as shown in FIG. 9F) is selectable during the process disclosed in Document 1, because it does not mention at all the growth rate of the composition semiconductor film growing by MOVPE. Therefore, a case, wherein the diode must be processed so as to have a suitable surface shape in accordance with its purpose, may be required later.
"Journal of Crystal Growth 145 (1994) p.622" (hereinafter referred to as Document 2) discloses highly uniform InGaAsP growth by MOVPE with atmospheric pressure which is another technique for manufacturing a semiconductor laser device.
Since InGaAsP grows uniformly according to the technique disclosed in Document 2, a surface of the grown film will be uneven when a base layer beneath is uneven. In other words, a planar surfaced film is unavailable on an uneven base. A case, wherein the completed semiconductor laser device must be processed so as to have a suitable surface in accordance with its purpose, may be required later.